8 This we have said in the case where the things done are similar. In the case where they are diverse, we find a man by charity made fierce; and by iniquity made winningly gentle. A father beats a boy, and a boy-stealer caresses. If you name the two things, blows and caresses, who would not choose the caresses, and decline the blows? If you mark the persons, it is charity that beats, iniquity that caresses. See what we are insisting upon; that the deeds of men are only discerned by the root of charity. For many things may be done that have a good appearance, and yet proceed not from the root of charity. For thorns also have flowers: some actions truly seem rough, seem savage; howbeit they are done for discipline at the bidding of charity. Once for all, then, a short precept is given you: Love, and do what you will: whether you hold your peace, through love hold your peace; whether you cry out, through love cry out; whether you correct, through love correct; whether you spare, through love do you spare: let the root of love be within, of this root can nothing spring but what is good.
Source: Homilies on the First Epistle of John (New Advent)